Plasma etcher with heated ash chamber base

ABSTRACT

A semiconductor manufacturing apparatus is described. That apparatus includes an ash chamber that has an ash chamber base, and a heating unit that is coupled to the ash chamber base. The heating unit applies heat to the ash chamber base to reduce deposition of residues onto ash chamber base surfaces, which could cause surface particle defects in a semiconductor device.

FIELD OF THE INVENTION

[0001] The present invention relates to semiconductor manufacturingapparatus, in particular equipment that includes an ash chamber forashing photoresist, when making semiconductor devices.

BACKGROUND OF THE INVENTION

[0002] To make a semiconductor device, several layers of different typesof material are deposited on a substrate, e.g., a silicon wafer. Someare metal layers that must be etched to create devices and interconnectsthat form the desired integrated circuits. A photolithography process isused to define the sections of the metal layers that must be removed.That process may include the following steps: depositing a layer ofphotoresist, masking portions of it, exposing the masked layer to lightthat has a selected wavelength, then developing the unexposed portions.This process leaves hardened photoresist over the sections of the metallayer that are not to be removed and exposes sections of the metal layerthat are to be etched.

[0003] After those exposed portions are etched, the remainingphotoresist must be removed. An ashing step is generally used to removethe photoresist. That step may require placing the wafer in an ashchamber, then exposing it to a plasma, which reacts with the photoresist(in effect, burns it up), removing it from the wafer surface.

[0004] To facilitate photoresist removal, the susceptor (upon which thewafer is mounted) may be heated. To ensure that this practice does notcrack or break the quartz bell jar that is positioned within the ashchamber base (hereinafter “ash base”), a coolant (e.g., water drawn froma municipal water supply) is typically circulated through the ash base.Circulating coolant through the ash base cools the ash base surfaces.Polymer residues (which comprise byproducts of the plasma generationprocess) may form on those cooled surfaces. Those residues can flake offthe ash base walls and drop onto the wafer. This can generate surfaceparticle defects that can ruin one or more of the semiconductor devicesthat are being formed on the wafer. In some cases, such particles cancause an interlayer dielectric (“ILD”), which is deposited over theetched metal layer, to tear as it is being polished. Such ILD tear outscan damage multiple die that are positioned adjacent to the one uponwhich the particle is lodged. As the critical dimensions for integratedcircuit devices continue to shrink, even very small particles can causefatal defects.

[0005] Accordingly, there is a need for an improved semiconductormanufacturing apparatus that reduces the number of semiconductor devicedefects that result from the photoresist ashing process. There is a needfor such an apparatus that reduces residue deposition on ash basesurfaces, thereby decreasing surface defects. The present inventionprovides such an apparatus.

BRIEF DESCRIPTION OF THE DRAWING

[0006]FIG. 1 represents a top view of a cross section of a plasma etcherthat may benefit from the present invention.

[0007]FIG. 2 represents a perspective view of an embodiment of thesemiconductor manufacturing apparatus of the present invention in whicha plasma etcher is coupled to a temperature control recirculating unit.

[0008]FIG. 3 represents a rear view of the temperature controlrecirculating unit of FIG. 2.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0009] The present invention relates to an improved semiconductormanufacturing apparatus. That device includes an ash chamber that has anash chamber base, and a heating unit. The heating unit is coupled to theash chamber base to apply heat to the ash chamber base to reducedeposition of residues onto ash chamber base surfaces, which could causesurface particle defects in a semiconductor device. In the followingdescription, a number of details are set forth to provide a thoroughunderstanding of the present invention. It will be apparent to thoseskilled in the art, however, that the invention may be practiced in manyways other than those expressly described here. The invention is thusnot limited by the specific details disclosed below.

[0010]FIG. 1 represents a top view of a cross section of a plasma etcher100 that may benefit from the present invention. Etcher 100 includesload cassette 101 for loading a wafer into load lock 102. From load lock102, the wafer is transferred to etch chamber 103. After an etchingoperation is performed, the wafer is transferred to ash chamber 104,where the ashing operation is carried out, then to unload lock 105, fromwhich the wafer is removed from etcher 100.

[0011] Current practice, which includes circulating relatively coolwater through the ash base, causes polymer residues to build up on theash base walls, as wafers are processed. Those residues may fall fromthose walls onto a wafer's surface, generating surface defects in one ormore die. The present invention reduces those defects by reducingresidue deposition on the ash base walls. An example of equipment thatcan serve to decrease residue build up is illustrated in FIG. 2. Here,plasma etcher 200 is coupled to heating unit 210. That plasma etcherincludes an etch chamber and an ash chamber—as shown in FIG. 1, and maybe one of many commercially available plasma etchers, such as the M300,M500, M600, and M700 series plasma etchers that are available fromHitachi America, Ltd. Heating unit 210 may be a commercially availabletemperature control recirculating unit, e.g., the Julabo® MD-4 or HE-4heating circulator, which is available from Julabo USA. That particularunit includes a heating element that can heat a fluid, e.g., water, to atemperature that is between about 20° C. and about 200° C., whilekeeping the temperature stable to within ±0.01° C.

[0012] As shown, heating unit 210 is coupled to the ash base of plasmaetcher 200 via conduits, e.g., tubes, 211. Those skilled in the art willrecognize that one end of tubes 211 can be hooked up to the ports, whichare located on the ash base, that currently are used to receive water tocool the ash base. The other end of those tubes can be hooked up toports that are located on the heating unit. In this embodiment, heatingunit 210 is located underneath a floor grating upon which etcher 200 isplaced. Tubes 211 pass through the grating to couple the etcher with theheating unit.

[0013] When the apparatus shown in FIG. 2 is put in use, a fluid iscirculated from heating unit 210 to the ash base. Heating unit 210 heatsthat fluid to a sufficient temperature to ensure reduction of residuedeposition on ash base surfaces (both on the bell jar and other exposedportions of the ash base) that could otherwise cause surface particledefects. The fluid may be water, which is maintained at a temperaturethat is at least about 50° C., and preferably between about 50° C. andabout 70° C. More preferably, the water temperature is maintained atabout 60° C. It may be desirable to limit temperature variation from theset temperature to ±1° C. or even ±0.1° C. In addition, when selecting60° C. for the water temperature, an upper alarm set point of about 62°C. and a lower alarm set point of about 55° C. may be desired. Toprotect against any damage that may result from excess temperature ofthe circulating water, the apparatus can be programmed to shut down whenit reaches a set temperature, e.g., a selected temperature that liesbetween about 65° C. and about 70° C. The apparatus may be shut downperiodically for preventive maintenance, e.g., after about 1,500 wafershave been processed through it.

[0014]FIG. 3 provides a rear view of the temperature controlrecirculating unit of FIG. 2. Heated water is delivered from unit 310 tothe ash base through tube 319 via connector 317. Heated water isreturned to unit 310 from the ash base through tube 320 via connector318. To accommodate varying tube diameters, adapters may be attached toconnectors 317, 318 that connect to tubes 319, 320 at one end and toconnectors 317, 318 at the other end.

[0015] In operation, water sent to the ash base may return at a highertemperature. To cool that returned water, cooling water (e.g., watertaken from a municipal water supply) can be delivered to unit 310through tube 321 via connector 315. That cooling water circulatesthrough the unit, then is dumped out tube 322 via connector 316.

[0016] The semiconductor manufacturing apparatus of the presentinvention reduces surface particle defects (e.g., those which may causeILD tear outs) by heating the ash chamber base. As a result, die yieldmay increase. Features shown in the above figures are not intended to bedrawn to scale, nor are they intended to be shown in precise positionalrelationship. Additional components that may be used to make thesemiconductor manufacturing apparatus of the present invention have beenomitted when not useful to describe aspects of the present invention.Although the foregoing description has specified certain features thatmay be included in such an apparatus, those skilled in the art willappreciate that many modifications and substitutions may be made.Accordingly, it is intended that all such modifications, alterations,substitutions and additions be considered to fall within the spirit andscope of the invention as defined by the appended claims.

What is claimed is:
 1. A semiconductor manufacturing apparatuscomprising: an ash chamber that has an ash chamber base; and a heatingunit, coupled to the ash chamber base, for applying heat to the ashchamber base to reduce deposition of residues onto ash chamber basesurfaces, which could cause surface particle defects in a semiconductordevice.
 2. The apparatus of claim 1 further comprising an etch chamber.3. The apparatus of claim 1 further comprising a conduit for circulatinga fluid between the ash chamber base and the heating unit.
 4. Theapparatus of claim 3 wherein the fluid is water.
 5. The apparatus ofclaim 4 wherein the heating unit includes a heating element that canheat the fluid to a temperature that is greater than about 50° C.
 6. Asemiconductor manufacturing apparatus comprising: a plasma etcher thatincludes an etch chamber and an ash chamber, the ash chamber having anash chamber base; and a heating unit, coupled to the ash chamber base,for applying heat to the ash chamber base to reduce deposition ofresidues onto ash chamber base surfaces, which could cause surfaceparticle defects in a semiconductor device.
 7. The apparatus of claim 6further comprising a conduit for circulating a fluid between the ashchamber base and the heating unit.
 8. The apparatus of claim 7 whereinthe heating unit includes a heating element that can heat the fluid to atemperature that is greater than about 50° C.
 9. The apparatus of claim8 wherein the fluid is water.
 10. A method of reducing residuedeposition onto ash chamber base surfaces comprising: circulating afluid from a heating unit to the ash chamber base; and heating the fluidup to a sufficient temperature to reduce residue deposition onto the ashchamber base surfaces.
 11. The method of claim 10 wherein the fluid iswater and the water is heated to a temperature of at least about 50° C.12. The method of claim 11 wherein the fluid is maintained at a selectedtemperature that is between about 50° C. and about 70° C.
 13. The methodof claim 12 wherein the fluid temperature is maintained within about 1°C. of the selected temperature.
 14. The method of claim 13 furthercomprising circulating a second fluid through the heating unit to coolthe water as it is returned from the ash chamber base.
 15. The method ofclaim 14 wherein the residues comprise byproducts of a plasma that isgenerated to remove photoresist from the surface of a wafer thatcontains partially made semiconductor devices.